I tend to trade 5lots a time. If im looking at going at mkt then it depends on the size which is on the bid/offer, but most the time I will always use limits and place bids and offers especially if I want a bigger position (10lots). Problems arise when you have stops and can get hit for slippage. From my experience 10 lots is not a big deal but do expect some slippage of a couple of ticks. If you looking for a more liquid mkt with better size than look at the estoxx.